The present invention concerns the field of immunotherapies in B cell neoplasms, in particular B cell lymphoma, including acute and chronic lymphocytic leukemias.
The incidence of B cell neoplasms is increasing, especially in Western Countries (NCI, SEER). Most cases of low grade lymphoma are diagnosed at advanced stages where no curative standard therapy is available. In chronic lymphocytic leukemia (CLL), there is still no established curative therapy available at any time point of diagnosis. In contrast, patients with high grade lymphoma or acute lymphoblastic leukemia benefit from intensive and potentially curative chemotherapy regimens. However, long-term prognosis is unfavourable for adult patients with recurrent disease. Thus, novel therapies are needed.
Immunotherapy has been shown to be highly successful in low grade lymphoma including CLL. There are target specific therapies using monoclonal antibodies which are directed against surface antigens as CD20 (Rituximab) and CD52 (Alemtuzumab) (1,2). However, tumor escape occurs due to down regulation of the target antigen from the cell surface. T cells are able to recognize peptides associated to MHC molecules derived from extra- and intracellular antigens. T cells are currently applied associated to allogeneic stem cell transplantation and responsible for a Graft versus leukemia effect (GvL effect) which has been shown to be present in different B cell neoplasms (3-5). However, one major disadvantage of this approach is Graft versus host disease (GvHD) due to transferred T cells non-specifically recognizing allogeneic MHC molecules. Using allorestricted peptide-specific T cells it might be possible to circumvent central tolerance against tumor-associated self-peptides and simultaneously dissociate beneficial graft versus leukemia effect from detrimental graft versus host disease (6,7).
Krackhardt et al., “Identification of tumor associated antigens in chronic lymphocytic leukaemia by SEREX”, Blood September 2002, vol. 100, no. 6, pages 2123-2131, describe the identification of KW13/FMNL1. Here, peptide-specific autologous T cells were generated recognizing one single FMNL1-derived peptide (TLLHYLVKV; SEQ ID NO: 21). However, it turned out that these T cells did not recognize tumor cells as described in the paper. Thus, it is likely that the specific peptide is not an epitope presented on the surface of CLL cells. Moreover, the specific peptide has not been listed. In addition, no specific TCR has been described.
The identification of an antigenic epitope, however is of fundamental importance to use a specific antigen as target for a therapeutic approach as tumor cells can be only targeted if the specific peptide is presented on the surface of a cell. Given a protein length of 1100 amino acids, there are 1091 different nonapeptides which can be used for pulsing and most of them may not bind to the restriction element and/or are not produced by the immune proteasome, thus they are mostly not presented on the surface of a tumor cell.
Mayr et al., “Transduction of CLL cells by CD40 ligand enhances an antigen-specific immune recognition by autologous T cells”, Blood November 2005, vol. 106, no. 9, compare the functional reactivity of T cell lines generated by stimulation with CD40OL-AAV-transduced CLL cells, GFP-AAV-transduced CLL cells as well as native CLL cells and CLL cells stimulated by CD40-Ligand. Their read-out is an ELISPOT-assay where they use peptide-pulsed APC using different peptides for pulsing. They claim that they have generated antigen-specific T cells. However, several important controls are missing in order to prove the significance of the peptides used for detection of specific antigen recognition, as for example peptides and well characterized T cells for positive and negative controls, peptide dilution and tetramer-staining of T cell lines. As CD40L-activated CLL cells may prime for many antigens and peptide-pulsed CLL cells can express many other antigens, peptide-specificity is not shown in the manuscript. Moreover, no specific peptide is mentioned concerning KW13. The authors merely mention “KW13” in the methods section. KW13 is actually not a peptide but the whole FMNL1 protein. In addition, no specific TCR has been discovered and described.
Thus regarding Mayr et al., no precise peptide has been described concerning KW13/FMNL1, no peptide-specificity has been proven, no epitope has been discovered, no specific TCR was shown. This is exactly the critical development which has been undertaken in our last work and which motivates us for the patent claims.